flask/label-pci: Allow specifying optional irq label

IRQs can be shared between devices, so using the same label as the PCI
device can create conflicts where the IRQ is labeled with one of the
device labels preventing assignment of the second device to the second
domain.  Add the ability to specify an irq label distinct from the PCI
device, so a shared irq label can be specified.  The policy would then
be written such that the two domains can each use the shared IRQ type in
addition to their labeled PCI device.  That way we can still label most
of the PCI device resources and assign devices in the face of shared
IRQs.

Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
Reviewed-by: Daniel P. Smith <dpsmith@apertussolutions.com>

docs/misc/xsm-flask.txt

@@ -205,6 +205,22 @@ parameter, which can also be changed using xl setenforce).  When using the
 default types for domains (domU_t), the example policy shipped with Xen should
 allow the same operations on or between domains as when not using FLASK.
 
+By default, flask-label-pci labels the device, I/O ports, memory and IRQ with
+the provided label.  These are all unique per-device, except for IRQs which
+can be shared between devices.  This leads to assignment problems since vmA_t
+can't access the IRQ devB_t.  To work around this issue, flask-label-pci
+takes an optional 3rd argument to label the IRQ:
+
+    flask-label-pci 0000:03:02.0 system_u:object_r:nic_dev_t \
+        system_u:object_r:shared_irq_t
+
+The IRQ labeling only applies to the PIRQ - MSI/MSI-X interrupts are labeled
+with the main device label.
+
+The policy needs to define the shared_irq_t with:
+    type shared_irq_t, resource_type;
+
+And the policy needs to be updated to allow domains appropriate access.
 
 MLS/MCS policy
 --------------

tools/flask/utils/label-pci.c

@@ -28,7 +28,7 @@
 
 static void usage (int argCnt, char *argv[])
 {
-	fprintf(stderr, "Usage: %s SBDF label\n", argv[0]);
+	fprintf(stderr, "Usage: %s SBDF label <irq_label>\n", argv[0]);
 	exit(1);
 }
 
@@ -39,12 +39,19 @@ int main (int argCnt, char *argv[])
 	int seg, bus, dev, fn;
 	uint32_t sbdf;
 	uint64_t start, end, flags;
+	char *pirq_label;
 	char buf[1024];
 	FILE *f;
 
-	if (argCnt != 3)
+	if (argCnt < 3 || argCnt > 4)
 		usage(argCnt, argv);
 
+	if (argCnt == 4) {
+	    pirq_label = argv[3];
+	} else {
+	    pirq_label = argv[2];
+	}
+
 	xch = xc_interface_open(0,0,0);
 	if ( !xch )
 	{
@@ -107,7 +114,7 @@ int main (int argCnt, char *argv[])
 	if (fscanf(f, "%" SCNu64, &start) != 1)
 		start = 0;
 	if (start) {
-		ret = xc_flask_add_pirq(xch, start, argv[2]);
+		ret = xc_flask_add_pirq(xch, start, pirq_label);
 		if (ret) {
 			fprintf(stderr, "xc_flask_add_pirq %"PRIu64" failed: %d\n",
 					start, ret);